The invention relates to a method of validating an operating diagnosis of a device, during which a succession of elementary diagnoses is performed to determine the normal or abnormal operation of the device.
The invention is advantageously applicable in the automobile field, and more particularly in the field of diagnosing onboard complex mechanical or electrical control devices in an automobile. However, the invention is more generally used in the field of the operational diagnosis of any more or less complex system for which a diagnosis is valid only when particular conditions are met.
Current vehicles include numerous more or less complex mechanical or electrical devices which are controlled by appropriate control devices, commonly called onboard computers, such as, for example, the device controlling the injection system of the engine, the device controlling an automatic or robotized gearbox, etc.
To ensure the safety of the users, on the one hand, and to facilitate the rapid repair in the event of failure by a repairer on the other hand, a control device incorporates diagnostic means, appropriate for rapidly detecting a failure of the device under test (the actual control device or the electrical or operational device controlled by the control device).
The term “failure” should be understood here to mean an operating fault, likely to lead immediately or ultimately to an abnormal operation of the device under test, or a failure characterized by an abnormal operation of the device under test. The failure can be continuous or intermittent.
The diagnostic means can be activated on a one-off basis, for example at the request of a repairer to check the operation of the device under test after a repair. The diagnostic means can also be active permanently, for example to continuously monitor the device under test and issue an alert when an abnormal operation is detected.
The diagnostic means implement the following method. Elementary tests are performed at predefined instants or in predefined situations (set of parameters of the device being monitored having a predefined value), for a predefined time or a predefined number of times. The result of each elementary test indicates either an elementary fault or a normal operation of the device being monitored.
A failure is confirmed when an elementary fault has been detected once or a predefined number of times. A fault code corresponding to the failure, and other quantities linked to the operation of the device under test are then stored in a fault memory of the diagnostic means.
This stored information is used subsequently by a repairer to identify the failure and the conditions in which the failure was confirmed. After an appropriate repair according to the diagnosed failure, the fault memory is reinitialized.
Finally, an operating test and a diagnosis of the device under test, then a new reading of the fault memory make it possible to confirm repair of the device by checking that the fault dealt with has not reappeared. For this, elementary tests are performed once or a predefined number of times, then the content of the fault memory is checked to check that the fault has not reappeared.
The drawback of this method is that it does not make it possible to guarantee that the diagnosis of the device under test has been performed completely, in particular in the case of an intermittent fault.